import java.util.HashSet;
import java.util.Set;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User:${USER}
 * Date:${YEAR}-${MONTH}-${DAY}
 * ${TIME}
 */
public class Main {
    public static void main(String[] args) {
        System.out.println("Hello world!");
    }
    public boolean containsDuplicate(int[] nums) {
        Set<Integer> set=new HashSet<>();
        for(int x:nums){
            if(set.contains(x))return true;
            set.add(x);
        }
        return false;
    }
}